A flash material having a better tortuosity and a method of making the same

Abstract

The application discloses a flash evaporation material with better tortuosity and a preparation method thereof, and belongs to the technical field of flash evaporation spinning. The preparation raw material of the flash evaporation material comprises polyethylene, the tortuosity is 2.5-25, and the permeability is 85-11800 mdarcy. The flash evaporation material provided by the application has suitable tortuosity, permeability, Gurley air permeability and hydrostatic pressure, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of flash spinning technology, specifically relating to a flash material with better tortuosity and its preparation method. Background Technology

[0002] Flash spinning is a process in which a polymer such as PE is dissolved in a spinning solvent to form a spinning solution, which is then extruded through a spinneret. Due to the rapid evaporation of the solvent, the polymer is re-solidified into fibers. The fibers are adsorbed onto a spinning screen to form a fiber web, which is then processed into a flash material through hot pressing and winding processes.

[0003] The polymer raw material currently used in flash evaporation is PE. Flash evaporation polyethylene nonwoven fabric has many excellent properties, such as excellent waterproof and breathable properties, excellent strength, tear resistance, puncture resistance, and burst resistance. Therefore, it is widely used in packaging materials, protective clothing, tarpaulins, printing substrates, and other fields.

[0004] Existing polyethylene flash evaporation materials are mostly prepared using traditional flash evaporation fiber forming processes. The fiber arrangement is highly random, and the connectivity and uniformity of the pores are difficult to control precisely, resulting in a discrete distribution of material tortuosity. When the tortuosity is too high, the fiber entanglement is too tight, the air permeability and moisture absorption path is extended, resulting in poor material permeability. When the tortuosity is too low, the fiber structure is loose, and the breaking strength and structural resilience deteriorate, making it difficult to meet application requirements. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a flash evaporation material with better tortuosity and its preparation method.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a flash material with better tortuosity, wherein the raw material for preparing the flash material includes polyethylene, with a tortuosity of 2.5 to 25 and a permeability of 85 to 11800 mdarcy.

[0008] In this invention, the tortuosity range of the preferred tortuosity is 2.5 to 25. When the tortuosity of the flash material of this invention meets the above requirements, the flash material is a flash material with preferred tortuosity.

[0009] The flash material provided by this invention has good tortuosity, which enables the material to have excellent strength and structural resilience while having better permeability.

[0010] In this invention, the tortuosity (abbreviated as τ) is a microstructural parameter that characterizes the complexity of the channel. It is defined as the dimensionless ratio of the actual migration path length l of the fluid particles to the straight-line distance L in the macroscopic thickness direction of the material, τ=l / L.

[0011] Permeability (abbreviated as k, unit mdarcy) is an intrinsic physical property parameter characterizing a material's ability to transport fluids. The calculation formula is:

[0012] k=(1 / F)×(d c 2 / 8);

[0013] d c The critical pore size (conductance-controlling pore throat-diameter) is determined by GB / T21650.1-2008 "Determination of pore size distribution and porosity of solid materials by mercury intrusion porosimetry and gas adsorption method - Part 1: Mercury intrusion porosimetry". It is the pore size corresponding to 50% of the total pore volume when the mercury ingress volume is 50%, also known as d. 50 ;

[0014] F is the formation factor, which is dimensionless, and the two together determine the permeation performance.

[0015] The tortuosity and permeability of the flash material described in this invention can be obtained using the same equipment. In this invention, the testing method for the tortuosity and permeability of the flash material includes: referring to GB / T21650.1-2008, using MicroActive AutoPore V9600 (Thermo Fisher Scientific), inputting the weighing weight value before testing, setting the pressure range to 0.1~61000 psia, and obtaining the values ​​of tortuosity and permeability.

[0016] The tortuosity of the flash evaporation material described in this invention is 2.5~25, for example 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 18, 20, 22, 23, 24, 25, etc., and the permeability is 85~11800 mdarcy, for example 85 mdarcy, 100 mdarcy, 200 mdarcy, 500 mdarcy, 800 mdarcy, 1000 mdarcy, 2000 mdarcy, 3000 mdarcy, 5000 mdarcy, 8000 mdarcy, 10000 mdarcy, 11000 mdarcy, 11800 mdarcy, etc.

[0017] As a preferred embodiment of the present invention, the tortuosity of the flash material is 2.5 to 5.

[0018] As a preferred embodiment of the present invention, the tortuosity of the flash material is 5 to 8.

[0019] As a preferred embodiment of the present invention, the tortuosity of the flash material is 8~11.

[0020] As a preferred embodiment of the present invention, the tortuosity of the flash material is 11-13.

[0021] As a preferred embodiment of the present invention, the tortuosity of the flash material is 13-15.

[0022] As a preferred embodiment of the present invention, the tortuosity of the flash material is 15-18.

[0023] As a preferred embodiment of the present invention, the tortuosity of the flash material is 18~21.

[0024] As a preferred embodiment of the present invention, the tortuosity of the flash material is 21~25.

[0025] As a preferred embodiment of the present invention, the permeability of the flash evaporation material is 85~3000 mD / Cy.

[0026] As a preferred embodiment of the present invention, the permeability of the flash evaporation material is 3000~6000 mD / Cy.

[0027] As a preferred embodiment of the present invention, the permeability of the flash evaporation material is 6000~9000 mD / Cy.

[0028] As a preferred embodiment of the present invention, the permeability of the flash evaporation material is 9000~11800 mdarcy.

[0029] As a preferred embodiment of the present invention, the Gurley permeability of the flash evaporation material is 1~40 seconds, for example, 1 second, 2 seconds, 5 seconds, 8 seconds, 10 seconds, 12 seconds, 15 seconds, 18 seconds, 20 seconds, 22 seconds, 25 seconds, 28 seconds, 30 seconds, 32 seconds, 35 seconds, 38 seconds, 40 seconds, etc. The testing standard for the Gurley permeability is TAPPI T-460 OM-21, and the testing method is: under a constant pressure difference of 1.22 kPa, measuring the passage of 100 mL of air through 6.45 cm. 2 Time (seconds) required for a circular sample.

[0030] As a preferred embodiment of the present invention, the hydrostatic pressure of the flash evaporation material is >80 cmH2O, for example 81 cmH2O, 90 cmH2O, 100 cmH2O, 120 cmH2O, 150 cmH2O, 180 cmH2O, 200 cmH2O, 220 cmH2O, 240 cmH2O, 250 cmH2O, 270 cmH2O, 280 cmH2O, etc. The hydrostatic pressure test standard is AATCC TM127:2017(2018)e:2019, and the test method is as follows: hydrostatic pressure is applied uniformly to one side of the sample at a rate of 60 mbar / min, and the test area is 28.3 cm². 2 Continue until three seepage points appear on the other side of the sample, and record the maximum hydrostatic pressure value at this time.

[0031] As a preferred embodiment of the present invention, the basis weight of the fibers in the flash evaporation material is 40~100 g / m². 2 For example, 40 g / m 2 50 g / m 2 60 g / m 2 70 g / m 2 80 g / m 2 90 g / m 2 100 g / m 2 wait.

[0032] In a second aspect, the present invention provides a method for preparing a flash evaporation material with better tortuosity as described in the first aspect, the method comprising:

[0033] S1. Dissolve the raw materials containing polyethylene in a spinning solvent to obtain a flash spinning solution;

[0034] S2. Flash spinning is performed on the flash spinning solution to obtain flash fibers;

[0035] S3. The flash fibers are web-laid, pre-opened, and hot-rolled to obtain the flash material with better tortuosity, wherein:

[0036] The pre-opening is performed using a group of punching rollers, which includes two oppositely arranged punching rollers with an inverted trapezoidal sawtooth array on their surfaces. The two punching rollers roll against each other with staggered tooth peaks and meshing. The equivalent linear pressure of the punching roller group is 295~785 N / cm.

[0037] The equivalent linear pressure P = F / W;

[0038] F represents the total applied pressure, in N;

[0039] W represents the roller length, measured in cm.

[0040] In this invention, the dotting roller assembly includes an upper roller and a lower roller. The surfaces of both the upper and lower rollers are provided with a serrated array. The serrations have an inverted trapezoidal structure (i.e., the longer side of the parallel opposite sides of the trapezoid is located on the side closer to the roller). When in use, the upper and lower rollers roll against each other and the tooth peaks are staggered and meshed. The staggered meshing of the tooth peaks means that when the upper and lower rollers mesh, the tooth peaks of the upper roller are aligned with the tooth valleys of the lower roller, and the tooth valleys of the upper roller are aligned with the tooth peaks of the lower roller, forming an alternating "peak to valley, valley to peak" meshing state.

[0041] This invention reconstructs the microstructure of the fiber network by pre-opening it using a perforated roller before heat setting, and limits the equivalent linear pressure of the perforated roller group to 295~785 N / cm, such as 295 N / cm, 300 N / cm, 350 N / cm, 400 N / cm, 450 N / cm, 500 N / cm, 550 N / cm, 600 N / cm, 650 N / cm, 700 N / cm, 750 N / cm, 780 N / cm, 785 N / cm, etc. This allows the fiber network formed by the fibers to be forcibly opened by the tensile shear coupling deformation field when passing through the meshing zone. At the same time, under the equivalent linear pressure limited by this invention, the critical untangling stress applied by the saw teeth to the fiber bundle is sufficient to destroy the weak connections between fibers, causing the fiber network to produce controllable plastic buckling and spatial rearrangement, forming a stable three-dimensional interwoven structure. The resulting flash material has superior comprehensive performance.

[0042] If the equivalent linear pressure is too small, the stress on the fiber bundle will be lower than the critical untangling strength of the fiber bundle. This will only result in a loose surface of the fiber web while the internal fiber nodes are not fully opened, leading to a low tortuosity of the final flash material, high permeability and air permeability, and low hydrostatic pressure.

[0043] If the equivalent linear pressure is too high, the stress on the fiber bundle will exceed the fiber yield strength, inducing brittle fracture of the fiber or molecular chain slippage damage. Although the local bulkiness is improved, the average fiber length decreases. It is difficult to form a stable mechanical anchor point during subsequent hot rolling and shaping, resulting in excessive tortuosity of the flash material and deterioration of material strength and structural resilience.

[0044] As a preferred embodiment of the present invention, the preparation method includes:

[0045] S1. Dissolve a polymer containing polyethylene in a spinning solvent, wherein the spinning solvent is any one or a combination of at least two of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, unsaturated hydrocarbons, halogenated hydrocarbons, alcohols, esters, ethers, ketones, nitriles, amides, fluorocarbons, sulfur dioxide, carbon disulfide, nitromethane, or water to obtain a flash spinning solution. Preferably, the polymer has a mass fraction of 7-12% in the flash spinning solution, for example, 7%, 8%, 9%, 10%, 11%, 12%, etc.

[0046] S2. Flash spinning the flash spinning solution to obtain flash fibers, preferably the flash spinning temperature is 205~225℃, such as 205℃, 208℃, 210℃, 212℃, 215℃, 218℃, 220℃, 222℃, 225℃, etc.

[0047] S3. Flash-evaporated fibers are laid into a web with a basis weight of 40~100 g / m². 2 After web laying, pre-opening and hot rolling are performed to obtain the flash evaporation material, wherein:

[0048] The pre-opening is performed using a group of punching rollers, which includes two oppositely arranged punching rollers with an inverted trapezoidal sawtooth array on their surfaces. The two punching rollers roll against each other with staggered tooth peaks and meshing. The equivalent linear pressure of the punching roller group is 295~785 N / cm.

[0049] Preferably, the hot rolling temperature is 125~155℃, such as 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, etc., the pressure is 120~900 N / cm, such as 120 N / cm, 200 N / cm, 300 N / cm, 400 N / cm, 500 N / cm, 600 N / cm, 700 N / cm, 800 N / cm, 900 N / cm, etc., and the speed is 10~50 m / min, such as 10 m / min, 15 m / min, 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min, etc.

[0050] Preferably, the spinning solvent is one or a mixture of two or more of the following: aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, unsaturated hydrocarbons, halogenated hydrocarbons, alcohols, esters, ethers, ketones, nitriles, amides, fluorocarbons, sulfur dioxide, carbon disulfide, nitromethane, water, and a main solvent and an auxiliary solvent. Preferably, the main solvent includes one or a mixture of two or more of dichloromethane (DCM), cis-1,2-dichloroethylene (cis-1,2-DCE), or 1,1-dichloro-1-chloroethane, and the auxiliary solvent includes one or a mixture of two or more of 1,1,1,3,3-pentafluorobutane, 1H-perfluoroheptane, and 1H,6H-perfluorohexane.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The tortuosity of the flash material provided by the present invention is 2.5~25, the permeability is 85~11800 mdarcy, and the overall performance is better;

[0053] (2) By utilizing the pre-opening process of the dotting roller, the present invention limits the equivalent linear pressure in the pre-opening process to 295~785 N / cm, which enables the obtained flash material to have suitable tortuosity and permeability. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the pre-opening process of the dotting roller described in an embodiment of the present invention. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Unless otherwise specified, the raw materials involved in the following specific embodiments of the present invention are all conventional materials in the art and can be purchased from commercially available products.

[0057] Example 1

[0058] This embodiment provides a flash evaporation material with better tortuosity and its preparation method, as follows:

[0059] (1) A flash spinning solution with a polyethylene mass fraction of 7% was prepared by dissolving polyethylene in a spinning solvent (DCM: cis-1,2-DCE: 1H,6H-perfluorohexane: 1H-perfluoroheptane in a mass ratio of 4:4:1:1).

[0060] (2) Flash spinning solution is subjected to flash spinning at a spinning temperature of 210℃ to obtain flash fiber;

[0061] (3) Flash-evaporated fibers are laid into a web with a basis weight of 65.2 g / m. 2 After the mesh is laid, pre-opening is performed using a group of barbed rollers, such as... Figure 1 As shown, the dotting roller assembly includes two dotting rollers with an inverted trapezoidal serrated array on their surfaces, which are arranged opposite each other. The two dotting rollers roll against each other with staggered tooth peaks. The equivalent linear pressure of the dotting roller assembly is 300 N / cm. Then, a hot rolling process is performed (temperature is 135.2℃, pressure is 230 N / cm, speed is 30 m / min) to finally obtain the flash evaporation material.

[0062] Example 2

[0063] This embodiment provides a flash material with better tortuosity and its preparation method.

[0064] The difference from Example 1 is that, in this example, the equivalent linear pressure of the dotting roller assembly is 460 N / cm.

[0065] Example 3

[0066] This embodiment provides a flash material with better tortuosity and its preparation method.

[0067] The difference from Example 1 is that, in this example, the equivalent linear pressure of the dotting roller assembly is 610 N / cm.

[0068] Example 4

[0069] This embodiment provides a flash material with better tortuosity and its preparation method.

[0070] The difference from Example 1 is that in this example, the equivalent linear pressure of the dotting roller group is 780 N / cm.

[0071] Comparative Example 1

[0072] This comparative example provides a flash material with better tortuosity and its preparation method.

[0073] The difference from Example 1 is that, in this comparative example, the equivalent linear pressure of the dotting roller assembly is 280 N / cm.

[0074] Comparative Example 2

[0075] This comparative example provides a flash material with better tortuosity and its preparation method.

[0076] The difference from Example 1 is that, in this comparative example, the equivalent linear pressure of the dotting roller assembly is 800 N / cm.

[0077] Performance testing

[0078] The flash materials provided in the examples and comparative examples were tested using the following methods:

[0079] (1) Tortuousness and permeability: Using MicroActive AutoPore V9600 (Thermo Fisher Scientific), input the weight value before testing, set the pressure range to 0.1~61000 psia, and obtain the values ​​of tortuousness and permeability;

[0080] (2) Gurley air permeability: The test method is based on the TAPPI T-460 OM-21 test standard;

[0081] (3) Hydrostatic pressure: The test method is in accordance with the AATCC TM127:2017(2018)e:2019 test standard;

[0082] The test results are as follows:

[0083] Table 1

[0084]

[0085] As can be seen from the examples and performance tests, the flash material provided by the present invention has suitable tortuosity, permeability, Gurley permeability and hydrostatic pressure, and has good application prospects.

[0086] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, the preparation method provided by the present invention, by limiting the equivalent linear pressure of the dotting roller group to 295~785 N / cm, enables the obtained flash material to have excellent comprehensive performance.

[0087] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A flash evaporation material with better tortuosity, characterized in that, The flash evaporation material is prepared from polyethylene with a tortuosity of 2.5-25, a permeability of 85-11800 mD / s, a Gurley permeability of 1-40 seconds, a hydrostatic pressure >80 cmH2O, and a basis weight of 40-100 g / m³. 2 ; The preparation method of the flash evaporation material includes: S1. Dissolve the raw materials containing polyethylene in a spinning solvent to obtain a flash spinning solution; S2. Flash spinning is performed on the flash spinning solution to obtain flash fibers; S3. The flash fibers are web-laid, pre-opened, and hot-rolled to obtain the flash material with better tortuosity, wherein: The pre-opening is performed using a group of punching rollers, which includes two oppositely arranged punching rollers with an inverted trapezoidal sawtooth array on their surfaces. The two punching rollers roll against each other with staggered tooth peaks and meshing. The equivalent linear pressure of the punching roller group is 295~785 N / cm. The equivalent linear pressure is the ratio of the total applied pressure F to the roll length W.

2. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 2.5~5.

3. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 5 to 8.

4. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 8~11.

5. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 11~13.

6. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 13~15.

7. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 15~18.

8. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 18~21.

9. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The tortuosity of the flash material is 21~25.

10. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The permeability of the flash evaporation material is 85~3000 mD / C.

11. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The permeability of the flash evaporation material is 3000~6000 mD / C.

12. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The permeability of the flash evaporation material is 6000~9000 mD / C.

13. The flash evaporation material with better tortuosity according to claim 1, characterized in that, The permeability of the flash evaporation material is 9000~11800 mdarcy.

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